Standardization works of international mobile telecommunication (IMT)-advanced which is a next generation (i.e., post 3rd generation) mobile communication system are carried out in the international telecommunication union radio communication sector (ITU-R). The IMT-advanced aims at support of an Internet protocol (IP)-based multimedia service with a data transfer rate of 1 Gbps in a stationary or slowly moving state or 100 Mbps in a fast moving state.
3rd generation partnership project (3GPP) is a system standard satisfying requirements of the IMT-advanced, and prepares LTE-advanced which is an improved version of long term evolution (LTE) based on orthogonal frequency division multiple access (OFDMA)/single carrier-frequency division multiple access (SC-FDMA) transmission. The LTE-advanced is one of promising candidates for the IMT-advanced. A technology related to a relay station is one of main technologies for the LTE-advanced.
The relay station is a device for relaying a signal between a base station and a user equipment, and is used for cell coverage extension and throughput enhancement of a wireless communication system.
When the relay station receives a backhaul downlink signal from the base station, there is an issue on which reference signal will be used to demodulate the backhaul downlink signal. For example, in order to demodulate control information of a control channel transmitted by the base station to the relay station, there is a need to know which reference signal is mapped to a radio resource region to which the control information is allocated.